This invention relates to nano-tube techniques, and more particularly to a method for manufacturing a nano-tube, a nano-tube manufactured thereby, an apparatus for manufacturing a nano-tube, a method for pattering a nano-tube, a nano-tube material patterned thereby, and an electron emission source having a patterned nano-tube material incorporated therein.
A field electron emission source is generally reduced in consumption of energy and increased in durability as compared with a thermion emission source which requires heating.
Materials currently used for manufacturing a field electron emission source include a semiconductor such as silicon or the like and metal such as Mo, W or the like, as well as a nano-tube. In particular, the nano-tube has a size and sharpness sufficient to permit concentration of an electric field and is chemically stable and increased in mechanical strength, resulting in being expected to provide a promising field electron emission source.
A nano-tube has been conventionally manufactured by laser abrasion, arc discharge between graphite electrodes in an inert gas atmosphere, chemical vapor deposition (CVD) using hydrocarbon gas or the like. In particular, a nano-tube manufactured by arc discharge techniques is reduced in defect in atomic arrangement, to thereby be particularly suitable for use for a field electron emission source.
Now, the conventional arc discharge techniques will be described.
A pair of graphite electrodes are arranged in a container in a manner to be opposite to each other and then the container is evacuated. Then, inert gas is introduced into the container and arc discharge is carried out therein. This results in an anode highly evaporating, to thereby produce soot, which is then deposited on a surface of a cathode. Generation of the arc is continued for several minutes or more. Then, the apparatus is caused to communicate with an ambient atmosphere, followed by removal or recovery of the thus-deposited material or cathode deposit from the cathode.
The cathode deposit is constituted by a soft core containing a nano-tube and a hard shell free of a nano-tube.
When the anode is made of graphite containing a metal catalyst, a nano-tube is contained in the soot.
Thereafter, the nano-tube is removed from the soft core and/or soot and then carried on a substrate so as to act as an electron emission source.
However, manufacturing of the nano-tube by arc discharge and manufacturing of the electron emission source which have been conventionally carried out cause problems.
More particularly, the prior art requires a vacuum container, a vacuum evacuation unit and an inert gas introduction unit, resulting in being relatively increased in equipment cost.
Another disadvantage of the prior art requires to repeat the evacuation and atmospheric communication, so that the prior art is time-consuming.
Also, the prior art requires recovery of the cathode deposit and/or soot and cleaning of the equipment after completion of the process, to thereby be unsuitable for continuous mass production of the nano-tube.
Further, manufacturing of the nano-tube produced by the prior art into the electron emission device has a disadvantage. More particularly, it requires many additional steps such as separation of the soft core and hard shell from each other, isolation of the nano-tube from the soot, purification of the nano-tube, carrying of the nano-tube on the substrate, and the like.
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a method for manufacturing a nano-tube which is capable of being highly readily practiced and suitable for continuous mass-production of the nano-tube.
It is another object of the present invention to provide a method for manufacturing an electron emission source which is capable of being readily practiced and suitable for continuous mass-production thereof.
It is a further object of the present invention to provide an apparatus for manufacturing a nano-tube which is capable of readily manufacturing a nano-tube.
It is still another object of the present invention to provide an apparatus for manufacturing a nano-tube which is capable of accomplishing mass-production of a nano-tube.
It is yet another object of the present invention to provide a method for manufacturing an electron emission source which is capable of readily manufacturing an electron emission source.
It is even another object of the present invention to provide an apparatus for manufacturing an electron emission source which is capable of attaining mass-production of an electron emission source.
It is another object of the present invention to provide a method for patterning a nano-tube material which is capable of readily patterning a nano-tube material with reliability.
It is a still further object of the present invention to provide a nano-tube which is capable of being readily manufactured.
It is a yet further object of the present invention to provide a nano-tube material which is capable of being readily and satisfactorily patterned.
In accordance with one aspect of the present invention, a method for manufacturing a nano-tube is provided. The method includes the step of arranging a first electrode and a second electrode in a manner to be opposite to each other in an air atmosphere. The second electrode is made of a material mainly consisting of a carbon material. The method also includes the steps of applying a voltage between the first electrode and the second electrode to carry out arc discharge therebetween and forming a carbon material on a predetermined region of the second electrode into a nano-tube due to the arc discharge.
In a preferred embodiment of the present invention, the first electrode is constituted by a torch electrode provided at an arc torch. The step of forming the carbon material on the predetermined region of the second electrode into the nano-tube due to the arc discharge is carried out while moving the torch electrode and second electrode relatively to each other.
In a preferred embodiment of the present invention, the second electrode is arranged on a surface of a substrate. The step of forming the carbon material on the predetermined region of the second electrode into the nano-tube due to the arc discharge is carried out while holding the substrate on a cooling member to cool the substrate through the cooling member.
In a preferred embodiment of the present invention, the step of forming the carbon material on the predetermined region of the second electrode into the nano-tube due to the arc discharge is carried out while surrounding at least the first electrode, the second electrode, and an arc discharge region between the first electrode and the second electrode with a surrounding member.
In a preferred embodiment of the present invention, the carbon material for the second electrode is any one selected from the group consisting of graphite, carbon, activated carbon, amorphous carbon and graphite.
In a preferred embodiment of the present invention, the carbon material for the second electrode is any one selected from the group consisting of a carbon material containing a metal catalyst, that having a metal catalyst formed on a surface thereof, that containing B and a metal catalyst, that having B formed on a surface thereof and that having B and a metal catalyst formed on a surface thereof.
In a preferred embodiment of the present invention, the metal catalyst is selected from the group consisting of Li, B, Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Y, Zr, Nb, Mo, Rh, Pd, In, Sn, Sb, La, Hf, Ta, W, Os, Pt, an oxide thereof, a nitride thereof, a carbide thereof, a sulfide thereof, a chloride thereof, a sulfate thereof, a nitrate thereof and a mixture thereof.
In a preferred embodiment of the present invention, the arc discharge is carried out while feeding specific gas to a region in which the arc discharge is generated.
In a preferred embodiment of the present invention, the specific gas is selected from the group consisting of rare gas such as Ar, He or the like, air, nitrogen gas, carbon dioxide gas, oxygen gas, hydrogen gas and a mixture thereof.
In a preferred embodiment of the present invention, the first electrode is made of a material mainly consisting of graphite, activated carbon and amorphous carbon.
In a preferred embodiment of the present invention, the arc discharge is generated by a DC or a DC pulse. The second electrode acts as an anode for the arc discharge.
In a preferred embodiment of the present invention, the arc discharge is generated by an AC or an AC pulse.
In accordance with another aspect of the present invention, a nano-tube is provided. The nano-tube is manufactured according to the method described above.
In accordance with a further aspect of the present invention, an apparatus for manufacturing a nano-tube is provided. The apparatus includes a first electrode and a second electrode arranged in a manner to be opposite to each other in an air atmosphere. The second electrode is made of a material mainly consisting of a carbon material, that containing a metal catalyst and that having a metal catalyst formed on a surface thereof. Also, the apparatus includes an arc generation means including a power supply for applying a voltage between the first electrode and the second electrode to generate arc discharge with respect to a predetermined region of the second electrode, resulting in a carbon material in the predetermined region being formed into a nano-tube due to the arc discharge, and a specific gas feed means for feeding specific gas to a region in which the arc discharge is generated.
In a preferred embodiment of the present invention, the first electrode is constituted by a torch electrode provided at an arc torch. The apparatus further includes a transfer means for moving the torch electrode and second electrode relatively to each other, so that a voltage is applied between the torch electrode and the second electrode while moving the torch electrode and second electrode relatively to each other, to thereby generate arc discharge with respect to a predetermined region of the second electrode, resulting in a carbon material on the predetermined region being formed into a nano-tube due to the arc discharge.
In a preferred embodiment of the present invention, the second electrode is arranged on a substrate. The apparatus further includes a holding means for holding the first electrode and second electrode while keeping the first electrode and second electrode spaced from each other at a predetermined interval. The holding means includes a cooling means for cooling the substrate.
In a preferred embodiment of the present invention, the apparatus further includes a surrounding means for surrounding at least the first electrode, the second electrode and an arc discharge region in which the arc discharge is generated between the first electrode and the second electrode.
In accordance with still another aspect of the present invention, a method for patterning a nano-tube is provided. The method includes the step of arranging a first electrode and a second electrode in a manner to be opposite to each other in an air atmosphere. The second electrode is made of a material mainly consisting of a carbon material. The method further includes the steps of applying a voltage between the first electrode and the second electrode to generate arc discharge therebetween; and forming a carbon material on a predetermined region of the second electrode into a nano-tube due to the arc discharge while moving the first electrode and second electrode relatively to each other.
In accordance with yet another aspect of the present invention, a method for patterning a nano-tube is provided. The method includes the step of arranging a first electrode and a second electrode in a manner to be opposite to each other in an air atmosphere. The second electrode is made of a material mainly consisting of a carbon material selected from the group consisting of a carbon material formed into any pattern-like shape, that containing a metal catalyst formed into any pattern-like shape and that having a metal catalyst formed into any pattern-like shape on a surface thereof; applying a voltage between said first electrode and said second electrode to generate arc discharge therebetween; and forming a carbon material on a predetermined region of the second electrode into a nano-tube due to the arc discharge.
In accordance with a still further aspect of the present invention, a method for patterning a nano-tube is provided. The method includes the steps of arranging a first electrode and a second electrode in a manner to be opposite to each other in an air atmosphere; arranging a mask of any opening pattern on a surface of the second electrode; applying a voltage between the first electrode and the second electrode to generate arc discharge therebetween; and forming a carbon material on a predetermined region of the second electrode corresponding to openings of the mask into a nano-tube.
In a preferred embodiment of the present invention, the first electrode is constituted by a torch electrode provided at an arc torch.
In accordance with a yet further aspect of the present invention, a nano-tube material is provided. The nano-tube material is patterned according to the patterning method described above.
In accordance with an even further aspect of the present invention, an electron emission source is provided. The electron emission source has the patterned nano-tube material described above incorporated therein.